I found a description of the game in Acorn User 17 (December 1983) but not much else. Reprinted here ... Hope it helps!

EMPEROR
The time of this wargame is the first four centuries AD. The player takes the part of the Emperor and he must pit his wits and forces against invading barbarians, rebellious provincials and treacherous Roman Generals. Even the Plebs of Rome will have to be placated with bread and circuses if the Emperor is to keep his head and his throne. If he can last out for the first eight years of the game he is judged on the state of the Empire at the end of that time. There are three levels of play. Depending upon his choice, the Emperor has to guide the Empire through the first, third and fourth centuries. To win in the first century he must expand the Empire by two provinces, in the third he must maintain his Empire intact and in the fourth he must lose not more than two Provinces. For each Province the player is given three items of information, the number of loyal Legions, the number of revolting Legions and the number of Barbarian Invaders of Local Rebels. During play Legions must be raised, taxes inflicted and troops moved. The choice of Generals can be very critical — some are loyal and good fighters, some are neither. Battles must be fought and invasions repelled. All the while the citizens in Rome must be kept happy and — you must keep an eye on those Barbarians in Britannia!